Subscriber line interface circuits (SLICs) are employed by telecommunication service providers to interface a communication wireline pair with subscriber (voice-data) communication equipment. In order to be able to be interfaced with a variety of telecommunication circuits including low voltage circuits providing digital codec functionality, the transmission channels of the SLIC must conform with a very demanding set of performance requirements, including but not necessarily limited to accuracy, linearity, low noise, filtering, insensitivity to common mode signals, low power consumption, and ease of impedance matching programmability,
Moreover, in a typical application, the length of the wireline pair to which a SLIC is connected can be expected to vary from installation to installation, and may have a significant length (e.g., on the order of multiple miles), transporting both substantial DC voltages, as well as AC signals (e.g., voice and/or ringing). As a result, it has been difficult to realize a SLIC implementation that has ‘universal’ use in both legacy and state of the art installations.